Cooling device capable of reducing thickness of electronic apparatus

ABSTRACT

A fan housing of a fan unit includes a housing wall standing from the surface of a printed circuit board. The printed circuit board serves to establish the fan housing in cooperation with the housing wall. The fan housing further includes a ceiling wall connected to the housing wall. The ceiling wall extends along a datum plane parallel to the surface of the printed circuit board. A high speed airflow can be generated within the fan housing. The airflow promotes the heat radiation from the printed circuit board. An electrically conductive wiring pattern extending over the surface of the printed circuit board may further promote the heat radiation from the printed circuit board.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a printed circuit board unitwith a cooling device in general incorporated within an electronicapparatus such as a portable digital assistant (PDA), a notebookpersonal computer, and the like. In particular, the invention relates toa printed circuit board unit comprising a printed circuit board, aventilation fan rotatable around the rotation axis intersecting theprinted circuit board, and a fan housing accommodating the ventilationfan.

[0003] 2. Description of the Prior Art

[0004] As disclosed in Japanese Patent Application PublicationP2000-77877A, a so-called fan unit includes a fan housing accommodatinga ventilation fan rotating around the rotation axis. When theventilation fan rotates, air is allowed to flow in the centrifugaldirection of the rotation axis. The fan housing serves to guide the airtoward the outlet. The air is discharged out of the outlet. At the sametime, air surrounding the fan housing is introduced into the fan housingthrough the inlet. The inlet is defined to face the surface of theprinted circuit board. When the air is sucked into the fan housing, airis allowed to flow along the surface of the printed circuit board.

[0005] In general, a number of electronic components are mounted on thesurface of the printed circuit board. The respective electroniccomponents protrude from the surface of the printed circuit board, sothat the electronic components hinder a smooth flow of the air. Theturbulence in the air is supposed to constrain the ventilation fan fromsucking the air into the fan housing. The suction quantity of the airmay be reduced. The ventilation fan suffers from reduction in thecooling efficiency. As the printed circuit board gets thinner, the spaceis reduced between the fan housing and the surface of the printedcircuit board. The cooling efficiency of the ventilation fan may stillget deteriorated.

SUMMARY OF THE INVENTION

[0006] It is accordingly an object of the present invention to provide aprinted circuit board unit with a cooling device contributing toreduction in the thickness of an electronic apparatus.

[0007] According to the present invention, there is provided a printedcircuit board unit with a cooling device, comprising: a printed circuitboard; a ventilation fan rotating around a rotation axis intersectingthe printed circuit board; a housing wall standing from a surface of theprinted circuit board at a periphery of the ventilation fan; and anoutlet defined in the housing wall.

[0008] The printed circuit board and the housing wall cooperate todefine a space for accommodating the ventilation fan. When theventilation fan rotates, the movement of air, namely, airflow can begenerated within the space. The printed circuit board and the housingwall lead the air toward the outlet. In this manner, the printed circuitboard can be utilized to form the cooling device.

[0009] In particular, a high speed airflow can be generated within thespace in the printed circuit board unit and the housing wall. Theairflow efficiently absorbs the heat from the surface of the printedcircuit board. The heat radiation from the printed circuit board can bepromoted. In general, an electrically conductive metallic wiring patternextends over the surface of the printed circuit board. The metallicwiring pattern usually has a superior heat conductivity as compared withthe material of the printed circuit board. The metallic wiring patternthus contributes to promotion of the heat radiation from the printedcircuit board. In particular, the metallic wiring pattern inside thehousing wall leads to an improved promotion of the heat radiation fromthe printed circuit board.

[0010] The printed circuit board unit of the aforementioned type mayfurther comprise: a ceiling wall connected to an upper end of thehousing wall and extending along a datum plane parallel to the surfaceof the printed circuit board; and an inlet defined in the ceiling wall.

[0011] In general, a number of electronic components are mounted on thesurface of the printed circuit board. The electronic components protrudefrom the surface of the printed circuit board. The electronic componentsis supposed to hinder a smooth flow of the air along the surface of theprinted circuit board. If the inlet is defined at a position spaced fromthe surface of the printed circuit board in the aforementioned manner, asmooth flow of the air can be established irrespective of the existenceof the electronic components. The air can smoothly be sucked into theinlet. A large quantity of the air can be sucked, so that the coolingefficiency of the cooling device can be improved.

[0012] For example, if the printed circuit board of the aforementionedtype is incorporated within an electronic apparatus, the inlet can beopposed to the inner surface of the enclosure of the electronicapparatus. Airflow can be generated along the inner surface of theenclosure in response to the suction of the air into the inlet. Ingeneral, a generally flat surface is defined on the inner surface of theenclosure. Less obstacles can be found on the inner surface of theenclosure as compared with the surface of the printed circuit board. Asmooth airflow can thus be generated along the inner surface of theenclosure. The air is smoothly sucked into the inlet. Since the air issmoothly introduced into the inlet in this manner, a higher coolingefficiency can be kept even when the space is reduced between the inletand the inner surface of the enclosure in the electronic apparatus. Thethickness of the electronic apparatus can reliably be reduced.

[0013] The printed circuit board unit of the aforementioned type mayfurther comprise an inlet defined in the printed circuit board insidethe housing wall. Air can be introduced not only from the space adjacentthe front side of the printed circuit board but also from the spaceadjacent the back side of the printed circuit board. A larger quantityof air can be sucked into the space defined by the printed circuit boardand the housing wall, so that the cooling efficiency of the coolingdevice can further be improved. Moreover, the front and back sides ofthe printed circuit board can simultaneously be cooled down enough. Itshould be noted that the inlet in the printed circuit board may beestablished in place of the inlet in the ceiling wall. This structurecontributes to a further reduction in the thickness of the electronicapparatus.

[0014] In addition, the printed circuit board unit of the aforementionedtype may further comprise: an electronic component mounted on theprinted circuit board; and an electrically conductive wiring patternextending over the surface of the printed circuit board inside thehousing wall and connected to the electronic component. The ventilationfan serves to promote the heat radiation from the electricallyconductive wiring pattern. The heat radiation from the printed circuitboard can still be improved. Moreover, since the electrically conductivewiring pattern is allowed to receive the heat from the electroniccomponent, the electronic component can efficiently be cooled down.

[0015] A heat radiation fin may be attached to the printed circuit boardand connected to the electronic component. The heat radiation finpromotes the heat radiation from the electrically conductive wiringpattern. The heat radiation fin may be located within the outlet.Alternatively, the heat radiation fin may be located to face the outlet.

[0016] An electronic component may be mounted on the printed circuitboard inside the housing wall. A high speed airflow can be generatedinside the housing wall based on the rotation of the ventilation fan inthe aforementioned manner. Accordingly, the electronic component canefficiently be cooled down. The electronic component may be locatedwithin the outlet, for example.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and other objects, features and advantages of thepresent invention will become apparent from the following description ofthe preferred embodiment in conjunction with the accompanying drawings,wherein:

[0018]FIG. 1 is a perspective view schematically illustrating a notebookpersonal computer according to an example of an electronic apparatus;

[0019]FIG. 2 is a plan view schematically illustrating the innerstructure of a main body and the front surface of a printed circuitboard unit;

[0020]FIG. 3 is an enlarged plan view schematically illustrating theback surface of the printed circuit board unit;

[0021]FIG. 4 is an enlarged plan view of a printed circuit board forschematically illustrating the main portion of a cooling deviceaccording to a first embodiment of the present invention;

[0022]FIG. 5 is an enlarged partial sectional view taken along the line5-5 in FIG. 2;

[0023]FIG. 6 is an enlarged partial sectional view, corresponding toFIG. 5, for schematically illustrating a modification of the coolingdevice;

[0024]FIG. 7 is an enlarged plan view, corresponding to FIG. 4, forschematically illustrating the structure of a cooling device accordingto a second embodiment of the present invention; and

[0025]FIG. 8 is an enlarged plan view, corresponding to FIG. 4, forschematically illustrating the structure of a cooling device accordingto a third embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0026]FIG. 1 illustrates a notebook personal computer 11 as an exampleof an electronic apparatus. The notebook personal computer 11 includes athin main body 12 and a display enclosure 13 coupled to the main body12. The display enclosure 13 is allowed to swing relative to the mainbody 12. Input devices such as a keyboard 14 and a pointing device 15are embedded in the surface of the main body 12. The user may utilizethe keyboard 14 and the pointing device 15 so as to manipulate thenotebook personal computer 11.

[0027] A liquid crystal display (LCD) panel module 16 is incorporatedwithin the display enclosure 13, for example. The screen of the LCDpanel module 16 is positioned in a window 17 defined in the displayenclosure 13. The user is allowed to observe the operation of thenotebook personal computer 11 based on texts and graphics, for example,displayed on the screen of the LCD display panel module 16. The displayenclosure 13 may be superposed over the upper surface of the main body12 through the swinging movement.

[0028] As shown in FIG. 2, a printed circuit board unit 18 isincorporated within the main body 12. The printed circuit board unit 18includes a printed circuit board 19 and a central processing unit (CPU)package 21 mounted on the front surface of the printed circuit board 19,for example. The CPU package 21 may include a small-sized ceramicsubstrate 22 and a CPU chip 23 mounted on the ceramic substrate 22, forexample. Not only the CPU package 21 but also various electroniccomponents 24 a, 24 b are mounted on the front surface of the printedcircuit board 19. An electrically conductive wiring pattern, not shown,is formed to extend over the front surface of the printed circuit board,for example. The electrically conductive wiring pattern serves toestablish electric connections between the CPU package 21 and theelectronic components 24 a, 24 b as well as between the electroniccomponents 24 a, 24 b.

[0029] Within the main body 12, a secondary battery 25 as well as a harddisk drive (HDD) 26 is connected to the printed circuit board unit 18,for example. The secondary battery 25 and the HDD 26 may be detachablyincorporated within the main body 12. The secondary battery 25 suppliesan electric power to the printed circuit board 18 in place of an ACpower supply, for example. The HDD 26 is allowed to hold applicationsoftware programs to be processed at the CPU chip 23 as well as variousdata utilized during the execution of the application software programs.

[0030] A cooling device 27 according to a first embodiment of thepresent invention is coupled to the CPU package 21. The cooling device27 includes a heat receiving plate 28, of a higher heat conductivematerial, superposed on the upper surface of the CPU chip 23. One end ofa heat conductive member such as a heat pipe 29 is connected to the heatreceiving plate 28. The other end of the heat pipe 29 is connected toheat radiation fins 31 attached to the printed circuit board 19. Heat ofthe CPU chip 23 is transmitted to the heat radiation fins 31 via theheat receiving plate 28 and the heat pipe 29. The heat radiation fins 31are allowed to protrude, out of a recess 32 defined in the printedcircuit board 19, into a space at the back of the printed circuit board19.

[0031] As shown in FIG. 3, electronic components such as a memory module35 including a random access memory (RAM), a PC card slot 36, a localarea network (LAN) module 37 are mounted on the back surface of theprinted circuit board 19. In this manner, relatively taller electroniccomponents are mounted on the back surface of the printed circuit board19 as compared with the front surface.

[0032] A fan unit 38 is further incorporated within the cooing device27. The fan unit 38 is attached to the back surface of the printedcircuit board 19, as shown in FIG. 3. The fan unit 38 includes a fanhousing 39 fixed to the back surface of the printed circuit board 19. Atop or ceiling wall 41 is defined in the fan housing 39. The ceilingwall 41 is allowed to extend along a datum plane parallel to the backsurface of the printed circuit board 19. An inlet 42 is defined in theceiling wall 41. The inlet 42 serves to interconnect the space insidethe fan housing 39 and the space outside the fan housing 39 to eachother.

[0033] Referring also to FIG. 4, a rotary member 43 is accommodatedwithin the fan housing 39. The rotary member 43 is designed to rotatearound the rotation axis CR extending in a direction perpendicular tothe back surface of the printed circuit board 19. Blades 44 areintegrally formed on the peripheral surface of the rotary member 43. Theblades 44 may be located at equal intervals, for example. The respectiveblades 44 are designed to extend in the centrifugal directions from therotary member 43. The individual blade 44 extends in a planeintersecting, by a predetermined inclination angle α, the vertical planeVP including the rotation axis CR. When the rotary member 43 rotates,the blades 44 serve to generate airflow in the centrifugal directionfrom the rotation axis CR. The rotary member 43 and the blades 44constitute a so-called fan or ventilation fan.

[0034] As is apparent from FIG. 4, a housing wall 45 is defined in thefan housing 39. The housing wall 45 is designed to stand upright fromthe back surface of the printed circuit board 19 at the periphery of theblades 44, so that the housing wall 45 mostly surrounds the ventilationfan. Specifically, the inner surface of the housing wall 45 is opposedto the outer ends of the blades 44 at positions spaced from the outerends of the blades 44. An outlet 46 is defined in the fan housing 39 atthe break of the housing wall 45. The outlet 46 is located to face theheat radiation fins 31. An inlet 47 is also defined in the printedcircuit board 19 inside the housing wall 45. The inlet 47 likewiseserves to interconnect the space inside the fan housing 39 and the spaceoutside the fan housing 39 to each other, in the same manner as theaforementioned inlet 42. Part of the printed circuit board 19constitutes the fan housing 39.

[0035] As is apparent from FIG. 5, the rotary member 43 is mounted on arotary shaft 51 extending in the vertical direction perpendicular to theback surface of the printed circuit board 19. The rotary shaft 51 isreceived on a bearing 52 fixed to the ceiling wall 41 of the fan housing39. A thin electric motor 53 is interposed between the rotary member 43and the bearing 52. The electric motor 53 may include permanent magnets54 attached to the rotary member 43, and stationary coils 55 fixed tothe bearing 52 and opposed to the permanent magnets 54. A controllerboard 56 is also fixed to the ceiling wall 41 of the fan housing 39. Acontroller circuit is established on the controller board 56. Thecontroller circuit operates to control the operation of the electricmotor 53.

[0036] Now, when an electric power is supplied to the electric motor 53,the rotary member 43 rotates around the rotation axis CR. The blades 44generate airflow in the centrifugal direction of the rotation axis CR.The generated airflow is guided along the housing wall 45 to the outlet46. The air is discharged out of the outlet 46 in this manner.

[0037] An opening 58 is defined in an enclosure 57 of the main body 12.The opening 58 is located to face the outlet 46 of the fan unit 38. Theair discharged out of the outlet 46 is allowed to flow through the heatradiation fins 31 and gets out of the main body 12 through the opening58. The air absorbs the heat from the heat radiation fins 31. In thismanner, the heat radiation from the heat radiation fins 31 isefficiently promoted.

[0038] A high speed airflow is generated based on the rotation of theblades 44 within the inner space surrounded by the printed circuit board19, the housing wall 45 and the ceiling wall 41. The airflow efficientlyabsorbs the heat from the surface of the printed circuit board 19. Theheat radiation from the printed circuit board 19 can be promoted. Ingeneral, an electrically conductive metallic wiring pattern extends overthe surface of the printed circuit board 19. The metallic wiring patternusually has a superior heat conductivity as compared with the materialof the printed circuit board 19. The metallic wiring pattern thuscontributes to promotion of the heat radiation from the printed circuitboard 19. In particular, the metallic wiring pattern inside the housingwall 45 leads to an improved promotion of the heat radiation from theprinted circuit board 19.

[0039] While the air is discharged out of the outlet 46 in theaforementioned manner, air is sucked into the fan housing 39 through theinlet 42. Since the inlet 42 in the ceiling wall 41 is opposed to theinner surface of the enclosure 57, airflow 61 can be generated along theinner surface of the enclosure 57 in response to the suction of the airinto the inlet 42. In general, a number of electronic components aremounted on the back surface of the printed circuit board 19. Theelectronic components protrude from the back surface of the printedcircuit board 19. The electronic components thus hinder a smooth flow ofthe air along the back surface of the printed circuit board 19. On theother hand, a generally flat surface is defined on the inner surface ofthe enclosure 57 of the main body 12. Less obstacles can be found on theinner surface of the enclosure 57. The smooth airflow 61 can begenerated along the inner surface of the enclosure 57 of the main body12. The air is smoothly sucked into the inlet 42. A large quantity ofthe air can be sucked into the fan housing 39, so that the coolingefficiency of the fan unit 38 can be improved. Since the air is smoothlyintroduced into the inlet 42 in this manner, a higher cooling efficiencycan be kept even when the space is reduced between the ceiling wall 41of the fan housing 39 and the inner surface of the enclosure 57.

[0040] At the same time, air can be sucked from the inlet 47 in theprinted circuit board 19 in the fan unit 38. The air is introduced intothe fan unit 38 not only from the space adjacent the back surface of theprinted circuit board 19 but also from the space adjacent the frontsurface of the printed circuit board 19. A still larger quantity of theair can be sucked into the fan housing 39, so that the coolingefficiency of the fan unit 38 can further be improved. Moreover, thefront surface of the printed circuit board 19 can be cooled down enougheven when the fan unit 19 is located on the back surface of the printedcircuit board 19.

[0041] When the inlet 47 is defined in the printed circuit board 19 inthe aforementioned manner, the ceiling wall 41 of the fan housing 39 maycompletely superposed over the inner surface of the enclosure 57, asshown in FIG. 6. Air can be sucked enough into the fan housing 39 fromthe inlet 47 irrespective of the closure of the inlet 42. A sufficientcooling efficiency can be maintained in the fan unit 38. This structureis supposed to contribute to an additional reduction in the thickness ofthe main body 12.

[0042]FIG. 7 illustrates a cooling device 62 according to a secondembodiment of the present invention. The cooling device 62 includes anelectrically conductive wiring pattern 63 extending over the frontsurface of the printed circuit board 19, and heat radiation fins 64attached to the front surface of the printed circuit board 19. Theelectrically conductive wiring pattern 63 is connected to a powerconsumption circuit, namely, the CPU package 21 and to the heatradiation fins 64. Soldering may be employed to fix the heat radiationfins 64 to the electrically conductive wiring pattern 63 on the printedcircuit board 19. The electrically conductive wiring pattern 63 mayfunction as a ground wire of the CPU package 21. It should be noted thatlike reference numerals are attached to the structure or componentsequivalent to those of the aforementioned first embodiment.

[0043] A fan unit 38 a is attached to the front surface of the printedcircuit board 19 in the cooling device 62. The fan unit 38 a may havethe structure identical to that of the fan unit 38 according to thefirst embodiment. The heat radiation fins 64 may be located within theoutlet 46 of the fan unit 38 a, for example. In addition, theelectrically conductive wiring pattern 63 is allowed to extend from theCPU package 21 to the heat radiation fins 64 inside the housing wall 45.

[0044] The cooling device 62 induces the heat radiation of a higherefficiency from the printed circuit board 19 based on a high speedairflow generated within the fan housing 39 of the fan unit 38 a in thesame manner as described above. The electrically conductive wiringpattern 63 promotes the heat radiation from the printed circuit board19. In addition, since the electrically conductive wiring pattern 63 isallowed to efficiently receive the heat from the CPU package 21, the CPUpackage 21 can efficiently be cooled down.

[0045] The air discharged from the outlet 46 is allowed to pass throughthe heat radiation fins 64. The air absorbs the heat from the heatradiation fins 64. The air thereafter gets out of the enclosure 57 ofthe main body 12 from the opening 58. The heat radiation from the heatradiation fins 64 can thus be promoted. Otherwise, any electricallywiring pattern for the ground of the electronic components 24 a, 24 bmay likewise be connected to the heat radiation fins 64.

[0046]FIG. 8 illustrates a cooling device according to a thirdembodiment of the present invention. The cooling device 66 likewiseincludes the aforementioned fan unit 38. Electronic components 67 aremounted on the back surface of the printed circuit board 19 inside thehousing wall 45 in the fan unit 38. The electronic components 67 may belocated at the outlet 46 of the fan unit 38, for example. The coolingdevice 66 of this type serves to promote the heat radiation from theelectronic components 67 based on a high speed airflow generated withinthe fan housing 39 of the fan unit 38 in the same manner as describedabove. It should be noted that like reference numerals are attached tothe structure or components equivalent to those of the aforementionedfirst embodiment.

[0047] The printed circuit board unit 18 along with the cooling device27, 62, 66 may be incorporated not only in a portable electronicapparatus such as the aforementioned notebook personal computer 11 and apersonal digital assistant (PDA) but also in a desktop type electronicapparatus. The bearing 52 for the rotary shaft 51 may be supporteddirectly on the printed circuit board 19 in the fan unit 38, 38 a.

What is claimed is:
 1. A printed circuit board unit with a coolingdevice, comprising: a printed circuit board; a ventilation fan rotatingaround a rotation axis intersecting the printed circuit board; a housingwall standing from a surface of the printed circuit board at a peripheryof the ventilation fan; and an outlet defined in the housing wall. 2.The printed circuit board unit with the cooling device according toclaim 1, further comprising an inlet defined in the printed circuitboard inside the housing wall.
 3. The printed circuit board unit withthe cooling device according to claim 2, further comprising: anelectronic component mounted on the printed circuit board; and anelectrically conductive wiring pattern extending over the surface of theprinted circuit board inside the housing wall and connected to theelectronic component.
 4. The printed circuit board unit with the coolingdevice according to claim 3, further comprising a radiation finconnected to the electrically conductive wiring pattern.
 5. The printedcircuit board unit with the cooling device according to claim 4, furthercomprising an electronic component mounted on the printed circuit boardinside the housing wall.
 6. The printed circuit board unit with thecooling device according to claim 1, further comprising: a ceiling wallconnected to an upper end of the housing wall and extending along adatum plane parallel to the surface of the printed circuit board; and aninlet defined in the ceiling wall.
 7. The printed circuit board unitwith the cooling device according to claim 6, further comprising aninlet defined in the printed circuit board inside the housing wall. 8.The printed circuit board unit with the cooling device according toclaim 7, further comprising: an electronic component mounted on theprinted circuit board; and an electrically conductive wiring patternextending over the surface of the printed circuit board inside thehousing wall and connected to the electronic component.
 9. The printedcircuit board unit with the cooling device according to claim 8, furthercomprising a radiation fin connected to the electrically conductivewiring pattern.
 10. The printed circuit board unit with the coolingdevice according to claim 9, further comprising an electronic componentmounted on the printed circuit board inside the housing wall.
 11. Theprinted circuit board unit with the cooling device according to claim 1,further comprising an electronic component mounted on the printedcircuit board inside the housing wall.
 8. An electronic apparatuscomprising: a printed circuit board; an electronic component mounted onthe printed circuit board; a ventilation fan rotating around a rotationaxis intersecting the printed circuit board; a housing wall standingfrom a surface of the printed circuit board at a periphery of theventilation fan; and an outlet defined in the housing wall.
 12. Theelectronic apparatus according to claim 11, further comprising an inletdefined in the printed circuit board inside the housing wall.
 13. Theelectronic apparatus according to claim 11, further comprising: anelectronic component mounted on the printed circuit board; and anelectrically conductive wiring pattern extending over the surface of theprinted circuit board inside the housing wall and connected to theelectronic component.
 14. The electronic apparatus according to claim13, further comprising a radiation fin connected to the electricallyconductive wiring pattern.
 15. The electronic apparatus according toclaim 11, further comprising an electronic component mounted on theprinted circuit board inside the housing wall.
 16. The electronicapparatus according to claim 11, further comprising: a ceiling wallconnected to an upper end of the housing wall and extending along adatum plane parallel to the surface of the printed circuit board; and aninlet defined in the ceiling wall.